The present invention relates to an integrated circuit device and an electronic instrument.
A display driver (LCD driver) is known as an integrated circuit device which drives a display panel such as a liquid crystal panel. The display driver is required to have a reduced chip size in order to reduce cost.
On the other hand, a display panel incorporated in a portable telephone or the like has approximately the same size. Accordingly, when reducing the chip size by merely shrinking the integrated circuit device (display driver) using a microfabrication technology, it becomes difficult to mount the integrated circuit device.
When the user manufactures a display device by mounting a display driver on a liquid crystal panel, various adjustments are necessary for the display driver. For example, it is necessary to adjust the display driver conforming to the panel specification (e.g. amorphous TFT, low-temperature polysilicon TFT, QCIF, QVGA, or VGA) or drive conditions, or to adjust the display driver so that the display characteristics do not vary depending on the panel. It is also necessary for the IC manufacturer to adjust the oscillation frequency or the output voltage or to switch to a redundant memory during IC inspection.
In related-art technology, the user adjusts the display driver using an external electrically erasable programmable read only memory (E2PROM) or an external trimmer resistor (variable resistor). The IC manufacturer switches to a redundant memory by blowing a fuse element provided in the integrated circuit device.
It is troublesome for the user to provide external parts, and a trimmer resistor is expensive, has a large size, and easily breaks. It is also troublesome for the IC manufacturer to blow a fuse element and then verify whether the integrated circuit device operates normally.
JP-A-63-166274 proposes a nonvolatile memory device which can be simply manufactured at low cost in comparison with a stacked-gate nonvolatile memory device which requires a two-layer gate. In this nonvolatile memory device, a control gate is formed of an N-type impurity region in a semiconductor layer, and a floating gate electrode is formed of a single-layer conductive layer such as a polysilicon layer (hereinafter may be called “single-layer-gate nonvolatile memory device”). The single-layer-gate nonvolatile memory device can be manufactured using a CMOS transistor process, since it is unnecessary to stack the gate electrodes.